The present invention relates to a tricycle including a pair of left and right front steerable wheels supported at a front portion of a vehicle body frame structure, and a single rear drivable wheel supported at a rear portion of the vehicle body frame structure, and particularly, to an improvement in a tricycle which can travel on a banking in an attitude in which the vehicle body frame structure is inclined in leftward and rightward directions along with the left and right front wheels.
The terms xe2x80x9cleftxe2x80x9d and xe2x80x9crightxe2x80x9d used in this specification mean the left and right in a state in which the vehicle body frame structure is turned forwards in an advancing direction of the tricycle.
Tricycles which are travelable on bankings are disclosed in, for example, Japanese Patent Application Laid-open Nos. 6-171569, 56-82681 and 1-229787.
In the tricycles disclosed in Japanese Patent Application Laid-open Nos. 6-171569 and 56-82681, the left and right front wheels are disposed to overhang largely from the turning axis. For this reason, it is extremely difficult to enhance the rigidity of support of the front wheels, while providing a reduction in weight of each portion or component, and if the rigidity of support is insufficient, it particularly results in lack of a stability in the banking travel. If the amount of overhanging of the left and right front wheels from the turning axis is large, an inertia moment of the steering system is increased, thereby making it difficult to carry out a light steering operation.
In the tricycle disclosed in Japanese Patent Application Laid-open No. 1-229787, the left and right front wheels are disposed on the turning axis, but a large number of expensive ball joints are used to support the front wheels in such a disposition. This brings about a reduction in rigidity of support of each of the front wheels, and makes it difficult to reduce the cost.
The present invention has been accomplished with such circumstances in view, and it is an object of the present invention to provide an inexpensive tricycle, wherein the rigidity of support of the left and right front wheels is high enough to enable banking travel, even if expensive ball joints are not used, and moreover, the steering operation can be conducted lightly.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a tricycle including a pair of left and right front steerable wheels supported at a front portion of a vehicle body frame structure, and a single rear drivable wheel supported at a rear portion of the vehicle body frame structure, wherein the tricycle comprises a cylindrical handle post which is fixedly mounted at a front end of the vehicle body frame structure and which turnably supports a steering shaft connected to a steering handlebar, left and right upper links which are integrally connected to each other and pivotally supported at an upper end of the handle post, left and right lower links which are integrally connected to each other and pivotally supported at a lower end of the handle post, a cylindrical left leg member which is pivotally supported at upper and lower opposite ends thereof to outer ends of the left upper and lower links, a cylindrical right leg member which is pivotally supported at upper and lower opposite ends thereof to outer ends of the right upper and lower links, a left front wheel support member rotatably supported on the left leg member, a right front wheel support member rotatably supported on the right leg member, the left front wheel being supported on the left front wheel support member and disposed immediately below the left leg member, the right front wheel being supported on the right front wheel support member and disposed immediately below the right leg member, and a steering operatively-connecting means being disposed below the handle post and both the leg members for operatively connecting the steering shaft and the left and right front wheel support members to each other.
According to a second aspect and feature of the present invention, there is provided a tricycle including a pair of left and right front steerable wheels supported at a front portion of a vehicle body frame structure, and a single rear drivable wheel supported at a rear portion of the vehicle body frame structure, wherein the tricycle comprises a cylindrical handle post which is fixedly mounted at a front end of the vehicle body frame structure and which turnably supports a steering shaft connected to a steering handlebar, left and right upper links which are independent from each other and pivotally supported at an upper end of the handle post, left and right lower links which are independent from each other and pivotally supported at a lower end of the handle post, a cylindrical left leg member which is pivotally supported at upper and lower opposite ends thereof to outer ends of the left upper and lower links, a cylindrical right leg member which is pivotally supported at upper and lower opposite ends thereof to outer ends of the right upper and lower links, a left front wheel support member turnably supported on the left leg member, a right front wheel support member turnably supported on the right leg member, left and right connecting frames which are fixedly mounted on at least ones of: the left and right upper links; and the left and right lower links, respectively, a connecting member which is turnably connected at opposite ends thereof to the connecting frames, the left front wheel being supported on the left front wheel support member and disposed immediately below the left leg member, the right front wheel being supported on the right front wheel support member and disposed immediately below the right leg member, and a steering operatively-connecting means being disposed below the handle post and both the leg members for operatively connecting the steering shaft and the left and right front wheel support members to each other.
The steering operatively-connecting means in each of the first and second features corresponds to a pit-man arm 31, a knuckle arm 32, a tie rod 33 and a ball joint 34 in embodiments of the present invention which will be described later.
With the first and second features, the left and right cylindrical leg members are pivotally supported at upper and lower opposite ends thereof by the left and right upper and lower links, and the left and right front wheels disposed immediately below the left and right leg members are supported by the left and right front wheel support members which are rotatably supported on the left and right leg members. Therefore, the left and right front wheels do not overhang sideways of the left and right leg members and hence, the rigidity of support of the left and right front wheels can be enhanced effectively in cooperation with the firm supporting of the upper and lower opposite ends of the leg members. As a result, it is possible to provide an enhancement in stability of the banking travel.
In addition, because the left and right front wheels do not overhang sideways of the left and right leg members, a reduction in inertia moment of the steering system is brought about, whereby the steering operation can be conducted lightly.
Further, since the steering operatively-connecting means for operatively connecting the steering shaft and the left and right front wheel support members to each other is disposed below the handle post and the left and right leg members, a wide space, which is free from interference of the steering operatively-connecting means, can be ensured in front of and above the handle post and the left and right leg members and hence, it is easy to place a carrier and the like.
Moreover, no ball joint is used in order to support the left and right front wheels, as described above, and hence, it is easy to ensure the rigidity of support of the front wheels, and it is possible to provide a reduction in cost.
According to a third aspect and feature of the present invention, in addition to the first or second feature, a left upright attitude maintaining means is provided between the handle post and one of the left upper and right links for exhibiting a spring force for returning the handle post to upright attitude thereof in response to the handle post inclining leftwards from the upright attitude, but for avoiding exhibiting a spring force, when the handle post is inclined rightwards from the upright attitude, and a right upright attitude maintaining means is provided between the handle post and one of the right upper and lower links for exhibiting a spring force for returning the handle post to upright attitude thereof in response to the handle post inclining rightwards from the upright attitude, but for avoiding exhibiting a spring force, when the handle post is inclined leftwards from the upright attitude, and a spring force for biasing the handle post in a direction toward the upright attitude being applied to the left and right upright attitude maintaining means even in the upright state of the handle post.
With the third feature, when the vehicle body frame structure has been inclined leftwards, a spring force for returning the vehicle body frame structure toward the upright attitude is applied to the vehicle body frame structure by the left upright attitude maintaining means. When the vehicle body frame structure has been inclined rightwards, a spring force for returning the vehicle body frame structure toward the upright attitude is applied to the vehicle body frame structure by the right upright attitude maintaining means. When the tricycle is at a stop in a non-ridden state, a driver can ride on the tricycle without anxiety in the upright attitude of the vehicle body frame structure. When the tricycle has been switched over from a turning traveling state with the vehicle body frame structure inclined, to a straight traveling state, the vehicle body frame structure is restored to the upright attitude, whereby the steerability can be further enhanced.